Yeah, considering 7 zip support is a good thing. Spacewise, here's how a fullset of roms, from 0001 to 0402 and some demos compressed: NDS(.zip): 8,11 GB (8.713.881.780 bytes) NDS(.7z & zip): 7,77 GB (8.345.866.837 bytes) NDsAfter(.7z): 6,45 GB (6.935.131.852 bytes) I know that in windows an Ultra.7z decompresses/compresses way faster than an Ultra.zip, but i don't know if this also happens when implementing it oneself.